Retrieving tool for well bores



June 23, 1959 G. W; WALTON ETA].

RETRIEVING TOOL FOR WELL BORES Filed Marh 9, 1954 hz E 17/57? 5 62-0265HZ 14 4421? ,Damuo L. M 6221) United States Patent 2,891,621 RETRIEVINGTOOL FOR WELL BORES George W. Walton, Dallas, Tex., and Donald L.McCarty, Milwaukee, Wis., assiguors to Ideco, Inc., a corporation ofOhio Application March 9, 1954, Serial No. 415,034

4 Claims. (Cl. 166-65) This invention relates to a retrieving tool forwell bores and particularly to a magnetic pick up tool adapted for usein removing paramagnetic objects or foreign bodies such as broken partsof drilling bits from the bottom of the bore. v

In order to facilitate the operation of such magnetic retrieving tools,it is desirable to eject fluid under pressure (such for example, asdrilling mud) into the bottom of the bore so that a fine suspension ofsolids is produced in that region to obviate interference by sand orother earthy material with the contacting of objects sought to beremoved by the magnet. This usually has been accomplished in the past byejecting such fluid away from the magnet through the most intenseportion of the magnetic field so that the pressure of the ejected fluidtends to retard the desired contact of the foreign bodies with themagnet and the desired adherence of such objects thereto.

The present invention overcomes the foregoing objections by providingfluid discharge passages which eject fluid into the bore through regionsof weakest magnetic intensity. At the same time, return fluid flowpassages from the bottom of the well bore through the tool are soarranged that such return flow is toward the magnet and is throughregions of greatest magnetic intensity thus assisting in bringing theforeign bodies into contact with the magnet. We further arrange toprovide pockets within such return flow passages by interposing passagednonmagnetic barriers. These pockets receive and assist in retainingsmaller objects picked up by the tool.

It is an important object, therefore, of the present invention toprovide a magnetic retrieving tool for well bores which is so arrangedthat the discharge of drilling fluid therefrom, while achieving thedesired results of producing a suspension of fine solids within thebottom of the well bore, does not interfere with, or oppose, the desiredaction of the magnet.

It is another important object of this invention to provide a magneticretrieving tool for well bores which has return fluid flow passages soarranged that the return flow of drilling fluid enhances and assists thedesired magnetic action.

It is a further object of such invention to so arrange the return flowpassage as to provide a pocket for the reception and retention ofsmaller objects picked up during the operation of the tool.

Other and further objects of the present invention will be apparent fromthe disclosures in the following specification and the accompanyingdrawings.

The invention (in a preferred form) is shown on the drawings andhereinafter more fully described.

On the drawings:

Fig. 1 is a central longitudinal section taken through a retrieving toolembodying the principles of the present invention; and

Fig. 2 is a bottom plan view of the tool shown in Fig. 1.

As shown on the drawings:

2,891,621 Patented June 23, 1959 In the specific embodiment of thisinvention chosen for purposes of illustration herein, the referencenumeral 10 indicates a head member which is provided with an internallythreaded socket 11 adapted for reception of a correspondingly externallythreaded drill pipe 12 by which the tool is moved into and out of thewell casing to the bottom of the well bore and through which fluid underpressure, such, for example, as drilling mud, is introduced into thebottom of the bore in a manner to be de scribed hereinafter. The headmember 10 which is made of steel is provided with an annular horizontalshoulder at an enlarged lower portion thereof, such shoulder beingdesignated by the reference numeral 13. The bottom of the recess orsocket 11 communicates with the lower face of the head member 12 forpassage of fluid under pressure through a plurality of passageways 14,two of which are shown in full lines in Fig. 1.

Abutting the shoulder 13 is the upper end of a cylindri cal casingmember 15 made of stainless steel or other non-magnetic strong metal ormetal alloy. The casing 15 is secured to the head member 10 by weldingas shown at 16 and by engagement of the upper end of the inner wall ofthe casing with a cylindrical portion 17 on the lower end of said headmember.

In firm contact with, and if desired suitably welded to, the lower faceof the head member 10 are a pair of permanent magnets 18 which may be ofgenerally semicylindrical cross-section and which are preferablysymmetrically arranged with reference to the axis of the cylindricalcasing 15 so that an annular passageway 19 is provided between the outerfaces of said magnets and the inner face of the cylindrical wall 15. Themagnets 18 are preferably composed of an alloy of aluminum, nickel andcobalt of high magnetic retentivity and as shown in Fig. 1 have theirinner parallel faces spaced from each other to form a passagewaytherebetween and also to provide the required gap between the poles ofthe magnet at the lower end of the casing, the magnetic circuit at theupper end of the casing being closed by the head member 10. The innerparallel faces of the magnets 18 are preferably covered by non-magneticstainless steel plates 18a welded to the top side of the pole shoes 24and extending to the head member 10 and Welded thereto. These platesseal off the annular fluid supply passage 19 from the return fluidpassage 20 and also permit of welding the space bar 21 in positionwithout affecting the magnetic properties of the permanent magnets 18.The gap or passageway between the magnet members 18 is designatedgenerally by the reference numeral 20 and this gap or passageway ispreferably closed by a passaged spacer or bar 21 of stainless steel orother non-magnetic material. The bar 21 is provided with a plurality ofapertures or small passageways 22 which afford a path for a return flowof drilling fluid in a manner to be described hereinafter. Thepassageway afforded by the gap 20 communicates fluid discharge throughthe lower portion of the head 10 by way of a plurality of passages 23which are so arranged as not to intersect the fluid inlet passages 14.

In order to assure of high magnetic intensity, the magnets 18 areprovided with pole pieces or plates in the form of a divided annularring 24 having a transverse opening or gap 25 communicating with the gapor return passageway 20 beneath the apertured spacer bar 21. The annularpole pieces or plates 24 tightly engage the inner wall of the casing 15near the lower end thereof and spaced inwardly therefrom for a purposeto be described hereinafter and where the plates 24 bridge the bottom ofthe annular recess 19, the said plates are provided'withia. plurality ofpassageways or apertures 26' which, in effect, are discharge passages orjets for the discharge of drilling 3 fluid introduced through thepassages 14 and the annular passage 19 into the bottom of the well bore.

The pole pieces or plates 24 are preferably made of magnetic steel ofhigh permeability to assure of high concentration of magnetic lines offorce at the opposed working poles of the magnet.

The pole pieces or plates 24 may be secured in association with thecasing 15 by welding or in any suitable manner, it being the purpose andintent of this invention that the assembled parts be held in rigidassociation.

As will be noted from an examination of Fig. l the lower end of thecasing 15 extends somewhat below the lower face of the pole pieces. Thislower end portion of the casing 15 is threaded as at 27 for reception ofa guide collar, mill or shoe (the use of which is optional). By havingthe casing 15 extend downwardly as shown for reception of such guidecollar. mill or shoe, it is obvious that magnetic leakage will beminimized.

In operation, the retrieving tool of this invention is lowered into thewell at the lower end of a string of drill pipes in the same manner aswould be the case with a drilling tool affixed to such drill pipe. Fluidunder pressure is pumped through the drill pipe into the socket i1 andhead and thence through the passages 14 into the annular passage 19,whence it is discharged through the jets or passages 26 into the bottomof the well bore to maintain the required fluid suspension at thatregion. If the lower edges of the casing 15 are not directly against thebottom of the well bore, fluid so discharged to a large extent returnsoutside of the casing 15 in an upward direction. If, however, the loweredges of the casing 15 or of a guide shoe or he like attached theretorest rather tightly against the bottom of the well bore, then the returnflow is largely through the passages 22 in the apertured spacer 21 andthence upwardly through the space and out through the passages 23.

Under intermediate conditions a portion of the r turn flow of fluiddischarged through the passages 26 is outside of the casing 15, while aportion thereof is back through the passage 20 and outlet passages 23.it will be appreciated that the region of greatest intensity of magneticflux and consequently of greatest attraction to objects to be retrievedby the magnet is in the area across the poles of the magnets 18 at thepole plate 24. Cousequently, by reason of the arrangement for fluid discharge which I have prepared, attraction of objects at this region isnot retarded by the outwardly flowing fluid under pressure. On the otherhand, the return flow toward that region enhances the movement ofobjects toward the magnet and furthermore smaller objects will becarried by that return flow and the magnetic attraction into the pocketbetween the lower ends of the magnets .8 and the apertured spacer 21,the apertures in that spacer being sufliciently small so that theobjects will not move therethrough. Since the vertical walls of thepocket are in a region of relatively high magnetic density, paramagneticobjects moved into the pocket by fluid flow and magnetic attraction willbe held in the pocket by the latter.

By reason of the arrangement of this invention, it is possible todischarge the required fluid under pressure into the bottom of the wellbore in such a way as not to interfere or impede the action of themagnet and the return flow of that fluid is so arranged as to enhancesuch action.

In this specification we have shown and described a preferred embodimentof our invention by way of example only, it being understood that anyarrangement of the magnet and casing whereby the outward flow of fluidunder pressure is in a region relatively remote from the region ofgreatest magnetic intensity and wherein the return flow of such fluid isthrough that region, may fall within the scope of this invention.

While the tool described herein is primarily intended for the removal ofparamagnetic objects from well bores, it may also be eflectively usedfor retrieving such objects from horizontal rock drill bores or otherbores bear ing varying angular relationship to the datum surface.Although primarily intended for use with a circulating fluid, the toolof this invention may also be used without such circulation in a dryhole where it is possible to bring the tool into position to directlyattract and hold the paramagnetic objects to be removed.

We claim as our invention:

1. in a magnetic retrieving tool for well bores, a head member having aninternal socket formed therein in the upper portion thereof throughwhich fluid under pressure is introduced into a well bore, a cylindricalcasing depending from said head member and forming a chamber, said headmember having a lower face extending across the upper end of saidchamber, a pair of permanent magnets in said chamber, said magnets beingsemi-cylindrical in cross-section and being symmetrically arranged toform an axial passage in said chamber, means supporting said pair ofpermanent magnets at said lower face, said pair of magnets being spacedradially inwardly of said casing to form together with said casing anannular passage in said chamber spaced outwardly of said axial passage,said head member having fluid-conducting means formed therein extendingbetween said internal socket and said annular passage to eject fluidthrough the tool, and additional fluid-conducting means extending fromsaid axial passage through said head member to the outside of said headmember so the flow of return fluid is through the tool at the region ofgreatest magnetic intensity.

2. in a magnetic retrieving tool for well bores, a head member having aninternal socket formed therein in the upper portion thereof throughwhich fluid under pressure is introduced into a well bore, a cylindricalcasing de pending from said head member and forming a chamber, said headmember having a lower face extending across the upper end of saidchamber, a divided annular ring having a transverse opening and tightlyengaging the inner wall of said casing near the lower end of saidchamber, a pair of permanent magnets supported by said divided annularring in said chamber at said lower face, said magnets being spacedradially inwardly of said casing and being spaced from one another toform an axial passage between said magnets and an annular passageconcentrically outwardly thereof, said head member havingfluid-conducting means formed therein extending be tween said internalsocket and said annular passage to eject fluid through the tool andhaving additional fluidconducting means extending from said axialpassage to the outside of said head member so the flow of return fluidis through the tool at the region of greatest magnetic intensity.

3. in a magnetic retrieving tool as defined in claim 2, an aperturedspacer bar in said axial passage above the lower end of said pair ofpermanent magnets to form a pocket receiving small articles washedthereinto by the flow of return fluid.

4. in a magnetic retrieving tool as defined in claim 3, said magnetshaving inner parallel confronting faces and having plates ofnon-magnetic material fastened thereto.

References Cited in the file of this patent UNITED STATES PATENTS2,431,361 Athy Nov. 25, 1947 2,556,849 Nolley et al. June 12, 19512,637,752 Ballew et al. Nov. 3, 1953 2,668,077 Kirby Feb. 2, 19542,709,104 Gibbs May 24, 1955 2,830,663 Kirby Apr. 15, 1958

